JPH0752922B2 - Ghost removal device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ghost elimination device, and more particularly to a TV (television) broadcast wave and various TV video devices and video devices that handle video signals obtained by detecting the same. The present invention relates to a ghost canceller that removes ghost and waveform distortion included in a video signal.

[Technical background]

Reflecting the recent trend toward higher image quality and larger screens in monitor devices for TV receivers, etc., high image quality TV broadcasting systems represented by high definition and clear vision are attracting attention.
On the other hand, ghost interference, which occurs due to simultaneous reception of reflected waves from skyscrapers and mountainsides, has become a new issue. Moreover, due to the increase in high-rise buildings, the disturbing area is expanding, and it is necessary to reduce or even eliminate it in the TV receiver on the receiving side. Especially, in high-quality TV receivers, It is required to mount a ghost removing device for removing ghost interference.

[Conventional technology]

In response to such a request, a reference signal for a ghost canceller is inserted in the NTSC system TV video signal. It is inserted in a predetermined line in the vertical blanking period and generates a reference pulse from this reference signal for use in the ghost removal operation. Hereinafter, regarding the method of generating the reference pulse, the signal waveform diagram of FIG. Will be explained together.

As shown in FIGS. 3 (A) to 3 (J), GCR signals {see (A), (C), etc. in the figure} and pedestal signals {see (B), (D), etc. in the figure} in field units. 2 signals of 4
Fields are separated and inserted in four phases, and eight fields are a repeating cycle. In FIG. 3, (A),
(C), (E), and (G) are even fields,
Each of (B), (D), (F), and (H) is an odd field. The bar waveform that serves as a reference signal for ghost cancellation is a GCR signal, and the pedestal signal is an auxiliary signal for removing the bar waveform by offsetting and removing the horizontal synchronizing signal and the burst signal by subtraction processing. GC
The R signal is inserted in the first, third, sixth and eighth fields {see FIGS. 3 (A), (C), (F) and (H) respectively},
The pedestal signal is inserted in the 2nd, 4th, 5th and 7th fields {Fig. 3 (B), (D), (E), respectively.
See (G)}.

In addition, in FIG. 3, the symbols "+" and "-" attached to the shoulders of the symbol "GCR" of the GCR signal and the symbol "0" of the pedestal signal are the polarities of the burst signals of the line (in the figure, Is also entered). As can be seen from FIG. 3, if the difference is obtained between the signals separated by four fields, the horizontal synchronizing signal and the burst signal are canceled and the bar waveform is extracted, as shown in FIG. it can. In order to use this as a reference signal, it is necessary to further pulse the ± GCR bar waveform by waveform conversion processing such as difference or differentiation as shown in FIG. The waveform extracted from the leading edge of this bar waveform is the reference pulse for ghost removal. This reference pulse contains a sufficient energy component up to 4 MHz.

FIG. 3 (L) shows the situation when the in-phase ghost occurs, and the error signal of FIG. 3 (N) obtained after subtraction of the reference waveform synchronized with the reference pulse (see FIG. 3 (M)). The operation principle of ghost removal is to obtain the delay time tg of the ghost, the amplitude value, etc. from the sequence (ε _n ) to determine the tap coefficient value of the transversal filter and set the weighting.

FIG. 2 is a block system diagram of a typical example of a conventional ghost elimination device having such an operation principle. In the figure, 8 is an A / D converter, 9 is a timing signal generation circuit, 11 is a filter section (FIR filter or Transversal filter consisting of IIR filter, etc., 12 coefficient setting circuit, 13 waveform acquisition circuit, 14 edge detection circuit, 15 synchronous addition circuit, 16 waveform conversion circuit, 17 subtractor, 18 reference waveform generator Circuit.
The timing signal generating circuit 9 generates a timing signal based on the horizontal synchronizing signal and the vertical synchronizing signal included in the input video signal, and supplies the timing signal to the reference waveform generating circuit 18 to generate the waveform capturing circuit 13 and the reference signal. It is synchronized with the waveform generation circuit 18. The following explanation will proceed in analog fashion,
Actually, the sampling frequency is, for example, 4 _SC ( _SC ≈ 3.58MH
z: color subcarrier frequency) shall be used for the signal system sampled.

In the conventional device 1 shown in FIG. 2, from the input line l ₁
The A / D converted input video signal X (t) is supplied to the filter unit 11. The filter unit 11 is composed of a recursive or non-recursive transversal filter, and its coefficient value is controlled by the coefficient setting circuit 12. The output from the filter section is taken out as an output video signal Y (t) via a line l ₂ and supplied to a waveform taking-in circuit 13 where a reference signal is included for a predetermined period (for example, one horizontal scanning line).
It is extracted (that is, waveform acquisition). The waveform acquisition circuit 13 can be configured by a delay circuit that delays the input signal by four fields, a subtracter (not shown) that subtracts the input signal and the delayed signal, and the like. As a result, FIG.
.. (H) to obtain a GCR bar waveform as shown in (I) or (J), and output it to the edge detection circuit 14 and the synchronous addition circuit 15 at the next stage. In the edge detection circuit 14, the midpoint of the leading edge of the GCR bar waveform is obtained from the maximum amplitude value position by the difference processing, and the GCR bar waveform periodically supplied for each field {in the case of FIG. Flip}
After aligning the waveform edges of, the synchronous addition circuit 15 performs synchronous addition.

The waveform conversion circuit 16 generates a pulse waveform as shown in FIG. 3K by a waveform conversion process such as difference or differentiation of the bar waveform as shown in FIG. , To the positive input terminal of the subtractor 17. That is, the leading edge portion of the bar waveform is used for generating the reference pulse, and this waveform includes the transmission characteristic from transmission to reception.

On the other hand, the reference waveform generating circuit 18 generates an original reference signal waveform (internal reference waveform) as shown in FIG.
Is being supplied to the negative input terminal of. Therefore, the subtractor 17 compares (subtracts) the waveforms of both signals and obtains a ghost-only waveform as shown in FIG. The result of this subtraction is output to the coefficient setting circuit 12 in the next stage as an error signal sequence ε _n . The coefficient setting circuit 12 has a function of determining the tap coefficient W _n of the transversal filter of the filter unit 11,
_{From n} , the following equation W _n ^{(ν + 1)} = W _n ^(ν) −α ^(ν) ε _n ^(ν) ………
(1) (however, ν is the number of times the processing has already been performed) is often performed in a sequential iterative manner. Also,
α is usually a constant (<1), but can be changed according to ν. Thus, the ghost component in FIG. 9 (N) is driven below the visual detection limit. That is, the video signal from which the ghost has been removed (reduced) is output from the filter unit 11. Since the coefficient setting circuit 12 requires an arithmetic function, it is composed exclusively of a microcomputer or a microprocessor.

Note that the circuit of FIG. 2 is an example of the configuration of feedback type control in which the reference signal is extracted from the output side of the filter unit 11 and the tap coefficient W _n is sequentially updated. There is feedforward type control which is performed from the input side of 11 and does not use the filter output by the past tap coefficient W _n to determine the tap gain. Either way, the random noise component contained in the reference signal portion of the input video signal is reduced by the synchronous addition circuit 15.

[Problems to be Solved by the Invention]

In the above conventional ghost removing device 1, the waveform capturing circuit 13
As a waveform acquisition function (method) in, the GCR bar waveform is extracted as a reference signal from the difference (subtraction result) between the signal at any given time and the signal 4 fields before (ie, 4 field delay signal). The clock may be disturbed due to the jitter included in the signal, the disturbance of the signal caused by the scene switching on the broadcast station side, or the impulse-like disturbance pulse noise, and the time accuracy of four fields may not be obtained. In such a case, the four-field difference becomes incomplete and a cancellation error occurs. When there is a ghost, it also affects that, and an unnecessary signal is output in a place where it should not exist. It will cause malfunction. Moreover, the conventional device has a problem that no protection or countermeasure is taken against such inconvenience.

[Means for Solving the Problems] The ghost removing device of the present invention has, in addition to the conventional configuration, a waveform check circuit inserted in a subsequent stage of the waveform capturing circuit,
In the waveform acquisition circuit, the reference signal separated by 4 fields is acquired and subtracted, and the GCR bar waveform obtained by canceling the horizontal synchronizing signal and the burst signal originally has a burst signal and this signal is canceled. In this period, both the condition that the squared integrated value of the data in this period does not exceed a certain value and the condition that the predetermined period that is originally a bar waveform has an amplitude above a certain value are satisfied. If any one of the two conditions is not satisfied, the GCR bar waveform is controlled by the waveform check circuit so as not to be used by the synchronous adder circuit and the edge detection circuit. Therefore, when an illegal signal state occurs, it is possible to prevent the signal from being sent to the edge detection circuit and the like in the subsequent stage to prevent malfunction. That is that to solve the problems. The determination as to whether the signal is normal or not is made by paying attention to the signal state in the output waveform of the waveform capturing circuit, particularly during the period when the burst signals are canceled.

〔Example〕

An embodiment of the ghost removing device of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a ghost removing device 10 of the present invention. In this figure, the same components as those of the conventional device shown in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. As is clear from a comparison between the two figures, in the ghost removing apparatus 10 of the present invention, the waveform checking circuit 20 is inserted between the waveform capturing circuit 13, the edge detecting circuit 14 and the synchronous adding circuit 15 to remove the ghost. Ten
Are configured. Since the other configurations and operations are the same as those of the conventional apparatus 1, description thereof will be omitted, and hereinafter, regarding the waveform check circuit 20 which is a new component, the signal waveform diagram (timing chart) of FIG. 5 will also be referred to. Will be described in detail.

FIG. 4 is a concrete circuit configuration diagram of the first embodiment of the waveform check circuit 20. In the figure, 21 multiplication circuits, 22 integration circuits, 23 and 25 comparison circuits, 24 absolute value conversion circuits, 26 and 27 NAND gate circuits (hereinafter simply referred to as "NAND circuits"), 28 flip-flop circuits , 29 is a delay circuit, and 30 is a gate circuit. The number of bits of the video signal handled here is 8 bits.

The ghost elimination reference signal supplied from the waveform acquisition circuit 13 to the waveform check circuit 20 is a waveform corresponding to FIG. 5 (A) or (B) {waveforms corresponding to FIG. 3 (I) and (J) respectively}. It is a GCR bar waveform like. As described above, the horizontal sync signal and the burst signal are canceled by taking the difference between the reference signals with the difference of 4 fields. When the sampling frequency is 4 _SC , the time difference of 4 fields is 9555000 (= 4
× 262.5 × 910) samples are also available, so it is usually VC
O (voltage controlled oscillator) is formed for stabilization.
However, due to the jitter contained in the video signal, the disturbance of the signal generated by the scene switching on the broadcasting station side, the impulse-like disturbance pulse noise, the ghost, etc., the clock and the synchronous reproduction system are disturbed and the time accuracy of 4 fields is reduced. It may not come out. Such is cancellation effect becomes inaccurate 4 field time difference becomes less satisfactory when, offsetting the rest and the burst signal as shown in FIG. 5 (C) to B _a, H _a
Beard of horizontal sync signal like. In particular, since the burst signal has a frequency of 3.58MHz, B _a is particularly likely to occur, and even if there is only one sample deviation, it is a fraction of the original burst signal.
Will come out. Therefore, in the first embodiment apparatus 10 was added inserting the waveform check circuit 20 detects the burst signal cancellation remaining B _a, normal input (GCR) signal, a means for determining an abnormal (abnormal) I'm using it.

Next, the specific operation of the main part of the ghost removing device 10 of the present invention will be described with reference to the signal waveform diagram of FIG. 5 along with the configuration of FIG. When the signal (GCR bar waveform) shown in FIG. 5A or 5B is supplied to both input terminals of the multiplication circuit 21 from the input line l ₃ , the squared value thereof is output. That is, by inputting the same data to the multiplication and multiplicand of the multiplication circuit 21, the square value of the data can be obtained. The data is assumed to be 2's complement 8 bits, for example. Here, when a signal including B _{a and the} like as shown in FIG. 7C is supplied to the multiplication circuit 21, its output is shown in FIG.
The waveform is as shown in and is supplied to the integrating circuit 22.
The integrating circuit 22 is supplied with the control signal G ₁ shown in FIG. (G), the integration time of {period t _a ~t _b in FIG (D)} The control signal G ₁ is Low level The integrated result is rounded to an appropriate number of bits (for example, 8 bits) and output. Therefore, when a signal having a waveform as shown in FIG. 6D is input, the output of the integrating circuit 22 becomes as shown in FIG. It should be noted that the integration of the squared values is cleared at the start of integration and after the integration is completed and the integration result is transferred to the comparison circuit 23. When the comparison circuit 23 detects a low pulse as shown in FIG. 3H, the comparison circuit 23 adds the squared value of the offset error of the burst signal obtained by the integration circuit 22 and the actual measurement in consideration of the S / N condition and the like. A comparison is made with the set value L _a determined from the value (see (M) in the figure). When the integrated value becomes larger than the set value L _a , a low level signal is sent to the NAND circuit 26,
Under other conditions, it outputs a High level signal.

On the other hand, the signal from the input line l ₃ (GCR bars waveform) is supplied as 8bit data to absolute value circuit 24. The actual configuration of the absolute value conversion circuit 24 includes seven 2-input EXOR (exclusive OR) circuits, and the input terminals of each EXOR circuit are
The remaining 7-bit signal lines except the MSB are connected bit by bit, and the MSB is commonly connected to the other input terminals. MSB
When = 1 (ie negative value), the input signal is inverted and the MSB
When = 0 (that is, a positive value), it is output as it is to the comparison circuit 25 in the next stage. The number of output bits is 7 bits as shown in FIG.

A control signal G ₂ as shown in FIG. 1I is supplied to the comparison circuit 25. When the control signal G ₂ is Low {period t _c / t _{d in} FIG. Whether or not the GCR bar waveform exists in its original form is compared with the set value L _b {see (E) in the figure}, and if there is any value smaller than this set value L _b , It sends a Low signal to the NAND circuit 26 and outputs a High signal under other conditions. By such an operation, the characteristics of the bar waveform are grasped. That is, in the NAND circuit 26, at least one of the outputs of the comparison circuits 23 and 25 is
Outputs a High signal when w is reached.

27 is also a NAND circuit, but this is NAN while the control signal G ₀ (reference signal instruction pulse) shown in FIG. 5 (F) is Low.
The Low signal is output to the flip-flop circuit 28 only when the High signal comes from the D circuit 26. Flip-flop circuit 28
Outputs its output in response to a clear pulse G ₃ (see (J) in the figure) generated from the leading edge of the reference signal instruction pulse G ₀ .
Set to Low, and preset the output line l ₅ to High only when a Low signal comes from the NAND circuit 27. When the output line l ₅ has any chance to High is that it has incoming reference signal not normal, At that time, interrupts the ghost canceling operation is performed repeatedly as usual periodic, measures such as to prevent malfunction Used for. It is also used to supply this signal to the synchronous adder circuit 15 in the next stage to control not to perform synchronous add.

The delay circuit 29 is for correcting the time delay that occurs in the signal processing system from the multiplication circuit 21 to the flip-flop circuit 28, and is set to the Low level time width T _{D of the} reference signal instruction pulse G _0. This is a delay time of about 1 line (1 horizontal scanning line). The gate circuit 30 is the delay circuit 29.
Output from the flip-flop circuit 28 is low.
And the control signal G ₄ (see FIG. 5 (K)) is Low level.
It is configured to output to line l ₄ only when. That is, if the output of the flip-flop circuit 28 becomes High and a reception state different from the normal state is reached, the level of the output line l ₄ is set to 0. Thus, in the normal reception state, the line l ₄ is shown in FIG.
The output will be as follows. In this case, the line
The input from l ₃ is the waveform shown in FIG.

The output of the waveform check circuit 20 having the above configuration and function is supplied to the edge detection circuit 14 and the synchronous addition circuit 15 via the line l ₄ , and thereafter, the same signal processing as the conventional circuit 1 is performed, but the coefficient Regarding the coefficient setting operation in the setting circuit 12, the output of the flip-flop circuit 28 is used, and the operation of the equation (1) is substantially set by setting the value of the coefficient α ^(ν) to 0 when the flip-flop circuit output is High. The sequential operation can be interrupted.

In this way, even if the TV signal is temporarily disturbed, it is possible to protect it, especially when the filter unit 11 is composed of a recursive transversal filter, which may cause divergence or oscillation. It becomes possible to sufficiently deal with the disturbance of the signal.

It should be noted that the output signal from the line l ₄ and the cutoff function in the gate circuit 30 in FIG. ₄ are functionally duplicated, so only one of them may be used, but in the specific configuration example shown in FIG. By utilizing both these functions, the stability is strengthened. Further, the above configuration can be effectively used depending on how to utilize the device 10 in the subsequent circuit.

Next, a second embodiment of the waveform check circuit will be described with reference to the circuit configuration diagram of FIG. 6 and the signal waveform diagrams (timing charts) of FIGS. 7A to 7N. In addition,
In FIG. 6, the same components as those of the first embodiment shown in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.
In the configuration in which the waveform check circuit 20 of the second embodiment is inserted and added, the burst signal cancellation residual B _a is detected and this is detected by the GC.
Although it has been used as a means for determining whether the R signal is normal or abnormal, it is possible that the front ghost component is superimposed on the burst signal cancellation period. Therefore, in this second embodiment, the burst signal is not the front ghost component. canceling the remainder a is a B _a and accurately detect, using this as a means for determining a normal, non-normal GCR signal.

Therefore, the filter circuit 31 is inserted in the preceding stage of the multiplication circuit 21, and only the remaining component of the burst signal cancellation is output to the multiplication circuit 21 of the next stage among the signals fetched through the line l ₃ . . Therefore, this filter circuit 31 is shown in FIG.
The center frequency is _SC (color subcarrier frequency) as shown in
BPF (band pass filter), or the front ghost component is considered to be the low frequency component, so an HPF (high pass filter) that cuts off frequencies below _SC as shown in FIG. Good to use. In the following description, the filter circuit 31 is assumed to be a BPF having a pass characteristic as shown in FIG. In this embodiment also, the data is assumed to be, for example, 2's complement 8 bits.

When a signal having a waveform as shown in FIG. 7C (substantially the same as in FIG. 5C) enters the filter circuit 31, its output is
The waveform as shown in FIG. 7D has the low-frequency component removed, and the waveform is supplied to the multiplication circuit 21 from both of its input terminals and squared, resulting in the waveform as shown in FIG. It is supplied to the integrating circuit 22. A control signal G ₁ as shown in FIG. 1I is supplied to the integrating circuit 22, and the control signal G ₁
There cumulative time of Low level {duration t _a ~t _b in FIG. (F)} is performed, the multiplication result a suitable number of bits (e.g. 8bi
t) to round and output. Therefore, when a signal having a waveform as shown in FIG. 6E is input, the output of the integrating circuit 22 becomes as shown in FIG. Regarding the integration of squared values,
Also, it is cleared after the integration is completed and the integration result is transferred to the comparison circuit 23. The comparator circuit 23, when detecting a low pulse as shown in FIG. 7 (J), and the integrated value of the squared value of the offset error of the burst signal obtained by the integrating circuit 22,
Set value L _a determined from the measured value with S / N conditions etc.
(See (F) in the figure). When the integrated value becomes larger than the set value L _a , the NAND circuit 26
, And outputs a high level signal under other conditions.

Thereafter, signal processing is performed according to the same operation principle as that of the circuit of the first embodiment, whereby a video signal in which the pre-ghost is satisfactorily removed can be obtained.

In the above description, the reference signal is extracted from the output side of the filter unit 11 to sequentially update the tap gain (that is, feedback type control), but the present invention is not limited to this, and the tap gain is determined. The reference signal is extracted by the filter unit without using the filter output by the past tap gain.
The ghost elimination apparatus of the present invention can be applied to any of the controls (that is, feedforward type control).

[Effect]

As described above, according to the ghost elimination device of the present invention, even if the ghost elimination device normally operates stably, the disturbance of the video signal due to occasional disturbance or the like and the signal generation side (transmission side of a broadcasting station etc.)
The signal disturbance due to the jitter that is constantly mixed in is detected by the level judgment in the burst signal cancellation period of the waveform after subtraction between the two reference signals of the four field time difference, and the level judgment of the bar waveform in the predetermined period is performed. Together with this, when a normal or abnormal signal comes in, it is possible to prevent malfunction or runaway by interrupting the ghost removal operation. In addition, since the determination of the above-mentioned two places also serves as a countermeasure against S / N, the device of the present invention can perform stable and reliable operation, and can be realized by adding a relatively small number of constitutions. Has features.

[Brief description of drawings]

FIGS. 1 and 2 are block configuration diagrams of the present invention and a conventional ghost removing device, respectively, and FIGS. 3A to 3N are signal waveform diagrams for explaining the operation of the device of the present invention and each part of the conventional device, and FIG. FIG. 6 and FIG. 6 are block diagrams showing the first and second embodiments of the concrete structure of the waveform check circuit which is the main part of the device of the present invention, and FIGS. 5 (A) to (M) show the waveform check circuit. First
Signal waveform diagrams for explaining the operation of each part of the embodiment, FIG.
(N) is a signal waveform diagram for explaining the operation of each part of the second embodiment of the waveform check circuit, and FIGS. 8 (A) and 8 (B) are pass characteristic diagrams of the filter circuit which can be used in the second embodiment circuit. 10 ... Ghost elimination device, 11 ... Filter section, 12 ... Coefficient setting circuit, 13 ... Waveform capture circuit, 14 ... Edge detection circuit, 15 ... Synchronous addition circuit, 16 ... Waveform conversion circuit, 17 ...
… Subtractor, 18 …… Reference waveform generation circuit, 20 …… Waveform check circuit, 21 …… Multiplication circuit, 22 …… Integration circuit, 23, 25 ……
Comparison circuit, 24 …… Absolute value conversion circuit, 26,27 …… NAND circuit, 2
8 …… Flip-flop circuit, 29 …… Delay circuit, 30 ……
Gate circuit, 31 ... Filter circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page Examiner Shuichi Sato (56) References JP-A-63-287267 (JP, A)

Claims (1)

[Claims] 1. A ghost elimination device for using a reference signal having an 8-field period, in which a GCR signal and a 0 pedestal signal are separated by 4 fields and arranged in 4 phases, for ghost detection, and which comprises a transversal filter. , A filter unit for removing ghost components in the input video signal by setting the tap gains thereof, and a predetermined period of time including a signal for a certain period including the reference signal included in the input video signal. A waveform capturing circuit for performing calculation in a manner, a synchronous adding circuit for synchronously adding signals for a certain period captured from the input video signal, a waveform converting circuit for converting a waveform of an output signal of the synchronous adding circuit, and the waveform A subtractor that compares the output of the conversion circuit with a preset reference waveform and outputs a signal corresponding to the comparison result, and a coefficient tap corresponding to the output of the subtractor. A coefficient setting circuit for setting a gain in the filter section, and an edge detection circuit for detecting an edge of the rectangular wave generated by the waveform acquisition circuit and supplying the output to the synchronous addition circuit and the coefficient setting circuit are provided. In the ghost elimination device, in the above waveform acquisition circuit, a burst signal originally exists in the GCR bar waveform obtained by canceling the horizontal sync signal and the burst signal by taking in and subtracting the reference signals separated by 4 fields. Moreover, in the period when this signal is supposed to be canceled, the condition that the squared integrated value of the data in this period does not exceed a certain value, and that the predetermined period when the bar waveform is supposed to be originally has an amplitude of a predetermined value or more When both of the conditions are satisfied, it is regarded as a normal state, and when any one of the two conditions is not satisfied, the GCR bar waveform is added to the synchronous addition. The waveform check circuit for controlling not to use in the circuit and the edge detection circuit, a ghost removal device, characterized in that inserted connected downstream of the waveform capture circuit.